code: def testRealCase(self):
      # a 5000 cycle sine wave should cross the zero line 10000 times
      filename = join(
          testdata.audio_dir, "generated", "sine_440_5000period.wav"
      )
      signal = MonoLoader(filename=filename)()
      wavzcr = ZeroCrossingRate(threshold=0.0)(signal) * len(signal)
  
      filename = join(
          testdata.audio_dir, "generated", "sine_440_5000period.mp3"
      )
      signal = MonoLoader(filename=filename)()
      mp3zcr = ZeroCrossingRate(threshold=0.01)(signal) * len(signal)
  
      self.assertAlmostEqual(wavzcr, 10000)
      self.assertAlmostEqual(wavzcr, mp3zcr)
  
file_path: essentia/test/src/unittests/temporal/test_zerocrossingrate.py
imports: from essentia_test import *
label_desc: Use image node_id 7 for calling the TestZeroCrossingRate obj's underlying member method code with example usage: obj.testRealCase() without return types